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Pulse code modulation compressor

  • US 4,037,226 A
  • Filed: 01/07/1976
  • Issued: 07/19/1977
  • Est. Priority Date: 01/07/1976
  • Status: Expired due to Term
First Claim
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1. A pulse code modulation compressor for companding pulse code modulation signals having a sign bit, comprising:

  • A. a magnitude comparator for comparing pulse code modulation signals having first and second inputs and decision outputs;

    B. a first shift register connected to said first comparator input and having an input;

    C. a memory having an address input and a pulse code modulation output programmed to convert compressed pulse code modulation signals to linear pulse code modulation signals, said memory output connected to said second comparator input;

    D. a second shift register having a single stage set of bit cells equal in number to the number of bits in a compressed pulse code modulation word and a sign bit cell to be processed, said word bit cells connected to said comparator decision outputs;

    E. a logic circuit connected between said magnitude comparator and said second shift register comprising;

    1. a first NAND gate having one input terminal connected to the sign bit at said magnitude comparator first input and another input connected to one said magnitude comparator decision output;

    2. a second NAND gate connected through an inverter to said sign bit at said magnitude comparator first input and having another input connected to another of said magnitude comparator decision outputs;

    3. a third NAND gate having an input connected to said first NAND gate and a second input connected to said second NAND gate and having an output connected to each bit cell of said address register except the most significant bit cell through a second inverter; and

    F. clock means connected to said second register to provide a series of successively more accurate memory address pulse code modulation words in said second register.

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